His slice comes from your hand, not the bowl
Kiwi flesh is a cheerful party food for a dog: sweet-tart, soft, and full of water and vitamin-rich goodness in a small package. The correct route for it at a children's birthday is hand to mouth — you take a slice, prepare it, and offer his portion deliberately. That is not fussiness. A dog allowed to graze the fruit salad bowl chooses his own menu from everything in it, eats far more sugar than anyone intended, and may reach the one ingredient in the bowl that turns a party into an emergency.
The grape warning comes first
Fruit salads at parties very often contain grapes, halved or whole, and grapes are seriously toxic to dogs — even a small number can cause kidney damage, and there is no reliable way to predict which dog will react worst. Raisins and currants in a salad carry the same danger. So the bowl is never his, not for one supervised mouthful, because a mouthful cannot be aimed. If you discover he has eaten grapes from a party bowl, do not wait for symptoms: call a vet straight away, because early treatment is what protects the kidneys, and 'he seems fine' is not a safe test with this particular fruit.
Peeling and portioning his kiwi
For the kiwi itself, peel away all the fuzzy skin — it is tough to digest and it is the surface that has been sprayed, shipped and handled. The pale core can stay or go; it is edible but firmer, so for a small dog cut it away with the skin for an easier chew. Slice the green flesh into small cubes rather than handing over a whole slice he might gulp. A few cubes is the portion for a medium dog, one or two for a small one: kiwi's fibre and acidity are gentle in that amount and considerably less gentle across half a fruit, announcing themselves as loose stools and a gurgly evening. A dog trying kiwi for the first time gets two cubes and a day's observation before it joins his known-fruits list.
Party management for a hopeful dog
Children drop food, carry plates at dog height, and feed friendly dogs as an act of love, so party rules need adults behind them. Settle him away from the food table with his own chew during the fruit course, brief the grown-ups that his treats come from one person only, and sweep the floor under the table before he is released back into the room — dropped grapes roll exactly where dogs look first. If party grazing has already happened by the time you find him under the table, reconstruct what was in the bowl before deciding how worried to be, and let the grape question drive the decision.
A party rule only works if every adult supervising him that afternoon has heard it, and parties are exactly where messages get lost between hosts, grandparents and helpers. Putting 'kiwi cubes from a hand, never the fruit bowl — grapes are dangerous' into his care notes in KinsLe through Care Teams gives everyone watching him the same short rule, in writing, before the first slice is cut.